w/Cdowns I think the body work is more important that the other 2, but it also depends on what you consider the best return would be. I don't know what other hobbies you have, but if you are into woodworking then the aircompressor could be a better investment since there are air tools for woodworking. If you are into metalworking, then you may want to go towards the welder. If you like to pressure washing everything insight, then that is what you should get.
Good luck with your decision and have fun.